In known art, as an apparatus that supplies fuel to an internal combustion engine such as a diesel engine, an accumulator fuel supply apparatus (common rail apparatus) has been used, which enables precise fuel injection through energization control of fuel injection valves by constantly supplying high pressure fuel to each fuel injection valve, the accumulator fuel supply apparatus being provided with a common rail to which a plurality of fuel injection valves are connected and in which high pressure fuel is accumulated.
This accumulator fuel supply apparatus is provided with a fuel tank, a low-pressure pump, a high pressure pump, the common rail, and the fuel injection valves. Note that, fuel inside the fuel tank is pumped up by the low-pressure pump, and the fuel is fed to the high pressure pump. The high pressure pump highly pressurizes the fuel and pressure feeds the fuel to the common rail. Consequently, the energization control of the fuel injection valves is performed and the fuel injection to the internal combustion engine is controlled in a state where high pressure fuel is supplied to each fuel injection valve.
Further, with this accumulator fuel supply apparatus, a flow rate of fuel fed to the common rail can be changed in accordance with a required rail pressure and injection quantity. The flow rate of fuel is adjusted by a flow rate control valve that is provided in a fuel passage that connects the low pressure pump and a pressurizing chamber of the high pressure pump. Furthermore, an overflow valve is provided in the fuel passage that leads to the flow rate control valve such that the flow rate of fuel is accurately adjusted by the flow rate control valve. Then, if the pressure of the low pressure fuel that is supplied to the flow rate control valve exceeds a predetermined value, some of the low pressure fuel is returned to the fuel tank through the overflow valve, and the pressure of the low pressure fuel that is fed to the flow rate control valve is maintained such that it does not exceed the predetermined value.
With regard to this type of accumulator fuel supply apparatus, various apparatus that adopt an electromagnetic low pressure pump as the low pressure pump have been proposed to improve startability of the internal combustion engine.
For example, as a fuel injection apparatus that starts fuel injection to the internal combustion engine promptly when the internal combustion engine starts, a fuel injection apparatus as shown in FIG. 12 has been disclosed (refer to Patent Document 1). This fuel injection apparatus is provided with fuel injection valves 302 that are installed in an internal combustion engine 301, injection control electromagnetic valves 303, a common rail 304, a high pressure pump 307, a fuel tank 308, a low pressure pump 309, and an ECU 311. After the ECU 311 determines that the internal combustion engine is to be stopped, if Pc≦P1, where Pc is a fuel pressure within the common rail 304 and P1 is a predetermined pressure, when an ignition switch is turned on, the ECU 311 determines that a driver has an intention to restart the internal combustion engine, and the ECU 311 pressure feeds pressurized fuel to the common rail 304 by operating the low pressure pump 309 until a starter switch is turned on.
Further, an accumulator fuel injection apparatus has been proposed, which can reduce an air quantity supplied into a fuel sump of the fuel injection valve from a pressurizing chamber of a supply pump via the common rail when the internal combustion engine is started, such that injection quantity metering is stabilized when the internal combustion engine is started. More specifically, a fuel injection apparatus has been disclosed (refer to Patent Document 2) as shown in FIG. 13, in which, when the internal combustion engine is started, as a target common rail pressure is low, even if a necessary pumping quantity of a supply pump 353 is lowered, there is no problem in terms of injection quantity metering accuracy. Therefore, a pressure control valve 356 is driven (opened) for a predetermined period of time when the internal combustion engine is started, such that fuel within a common rail 351 is discharged from the pressure control valve 356 into a fuel tank 355 via fuel return flow paths 363, 364 and 365, and air entered into the supply pump 353 is discharged from a high pressure fuel path when a vehicle is left standing for a long period of time after stopping the internal combustion engine.    Patent document 1: Japanese Patent Application Publication No. JP-A-8-121281 (all text and all figures)    Patent document 2: Japanese Patent Application Publication No. JP-A-2003-239823 (all text and all figures)